Traditional Methods for Precision Backcountry Navigation
Terrain Association, Observational Navigation, Map and Compass
By Paul Repak
The ability to travel safely, confidently, and independently in wild and remote outdoor places requires practiced skills with knowledge of your surroundings, your tools, and yourself. The art and science of precision land navigation is not difficult if taken one step at a time, anyone can master it but field practice is necessary to build confidence and skill. Details of teaching advanced methods and techniques may vary but the philosophy is the same – observe the surrounding environment, use a few simple tools, let your mind process information and work with nature's available clues to find your way in the woods. This tutorial focuses on basic traditional methods that have been successfully applied by woodland and mountain navigators for decades and much longer. It doesn't really matter whether you are following a familiar long established trail or are bushwhacking your own virgin path through dense woods. The same techniques apply on or off trail. You can know where you are hiking to high accuracy at any given moment of time and at any place in the wild backcountry. "We do not go to the green woods and crystal waters to rough it, we go to smooth it. We get it rough enough at home, in towns and cities." - Nessmuk (G.W. Sears)
Navigation methods of terrain association, observational navigation, dead reckoning, map reading, and map with compass all require you to interact with the environment using very simple tools. Singularly or together, they require thought and planning at many levels, all of which will become automatic with time and practiced experience. It is natural to feel apprehensive until sufficient skills develop. In the end there is a deep internal satisfaction that comes from planning and successfully navigating to any place in the wilderness by any route you choose to explore by using the clues nature gives you along with your ability to assemble them logically. You will be able to find your way and pinpoint your location on the earth with precision and confidence. Interacting with the environment is, after all, why we go to the woods and mountains in the first place. "In every walk with nature one receives far more than he seeks." - John Muir
A word about GPS receivers – the methods of this instruction do not assume or expect that you have one. Integrating use of a hand held GPS receiver as a supplemental tool with these techniques is left to other articles that use these learned primal skills as a basis. GPS use is considered only as an additional tool in a navigator's kit. GPS being a special case of a satellite radio receiver it is never a replacement for basic backcountry navigation methods and skills. At least while you are learning, the more you can resist relying on a GPS to bail you out of temporary confusion, the better and quicker you will master traditional navigation techniques free of the need for electronic radio reception. The most important navigation tool is in your head. Anything else, including map or compass, is just an additional aid. Entering a remote backcountry wilderness with a GPS receiver as the only navigation means without also understanding the more basic navigation methods available to you is flatly unwise and insanely unsafe, period. "For the things we have to learn before we can do them, we learn by doing them." - Aristotle
You need to have only limited previous hiking experience to begin learning basic land navigation. The approach here is to introduce navigation by observational methods along with map interpretation of the terrain. For ease of understanding, the all-important magnetic compass discussion is left until after visual observation and terrain association techniques are mastered. To get a handle on map reading methods it is sufficient (for now) only to know how to tell roughly which way is north (and E, S, W) by glancing at a magnetic compass and roughly correlate those directions with the map. Much more on compass use will follow later in the detailed compass section.
It is assumed you can recognize the general features and symbols depicted on a topographic map in areas typical of recreational hiking terrain, including forests, lakes, trails streams, wetlands, hills, valleys, and mountains. By observing contour lines in detail, the five major terrain land features (hilltop, valley, ridge, depression, and saddle) can be determined and used to the navigator's advantage. You should now or very soon understand how to interpret contour lines and be able to roughly visualize in 3D their shapes and gradients relating to terrain land and water features, slopes, and elevations as represented by a topographic map.
If you are new and uncomfortable to understanding land navigation techniques, start slow and do not bite off too much at first. Find a "safe" familiar landscape you already know close to home. A large suburban park or small public forest area with distinct boundaries and a number of varied terrain features (that could include slopes, ravines, streams, and ponds) along with a USGS topographic map of the area would be ideal. Do not fear becoming "lost" in such a place, instead seek out the experience and understand how to handle the apprehensive feelings when even a little disoriented and confused. Experience is the best teacher, from which you learn much only as long as afterwards you review and determine what missed clues and mistakes led you into the temporarily confusing situation. You might begin to make the same mistakes again later, but they will occur less frequently and you will have learned to more quickly recognize and prevent them. "A person who never made a mistake never tried anything new." - Albert Einstein
You can't get there from here if you don't know where "here" is. To know where you are going you must first know where you are. That process starts at home long before you pack up and drive to the trailhead. Decide where you want to go and what you want to see and experience along the way. Choose routes, destinations and trip goals for whatever reason and by whatever means suits you (recommendations, guidebooks, or random curiosity about a remote bit of rock), then figure out how you will get there. The end goal and route chosen must among other factors consider things such as safety and emergency escape issues, terrain difficulty, participant physical abilities and outdoor skills, required equipment, and of course the natural views along the way. "Focus on the journey, not the destination. Joy is found not in finishing an activity but in doing it." - Greg Anderson
Obtain detailed (7.5 minute series, either 1:24K or 1:25K scale) topographic maps covering the entire planned route plus any possible side trips and safety exit routes. Either the traditional USGS paper maps, or your favorite equivalent in computer software will do (you will have to print out a paper copy to take with you). It is important to realize that your route and destination plans are dynamic, subject and likely to change before and after you get to the field due to many factors. That's okay, it's an unavoidable part of the planning and execution process and overall makes the trip more interesting. Just take that into account with a flexible plan, expecting changes to occur. Often an overly ambitious plan is wisely cut short at second thought. Better that than overextending your abilities, and also better that than making up new far flung destinations as-you-go because you had an overly simple plan. The single greatest cause of unhappy backcountry trips is poor or inadequate planning, and the single greatest planning mistake is being determinedly overly ambitious on distance and physically demanding goals. "Adventure is just bad planning." - Roald Amundsen
So you now have chosen an interesting destination a few miles away from an associated hiking trailhead or bushwhack departure point. You can't start walking in a straight line with your eyes closed and hope to arrive at your destination, nor would you want to. You will be enjoying the sights of the wilderness environment and landscape with every footstep, at the same time looking for navigation clues to keep yourself within a narrow range of bounds on the planned route to the destination. Absorbing the natural outdoor wonders while observing the terrain for navigation are both part of the same process. At intervals you will have certain built-in predetermined route milestone checkpoints, perhaps a trail intersection or a place where you leave the trail to begin a bushwhack. Some checkpoints will be unmistakably distinctive terrain landmarks or trail features; others may be more obscure and not so readily obvious to the untrained eye. Certain of these locations on your route may require you to take action to alter course. A "blind" checkpoint may not even be observable; it exists only as a timed turning point. Others are just unmistakable natural navigation points easy to recognize. These unmistakable points are your major planning checkpoints, your milestones and known precise position resets that verify you are not going astray or becoming disoriented. They help you reach a destination by breaking up the route into individual manageable segments with defined beginnings and ends. "May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view. May your mountains rise into and above the clouds." - Edward Abbey
On a trail a checkpoint could be a major bend or change in trail direction, a bridge, an intersecting trail junction, or an isolated boulder you read the trail guide says is at the hairpin bend in the river. You can define a checkpoint where the route approaches close to a cliff, the bottom of crossing a ravine, the crest of a knoll, or the lower end of a descending ridge. Perhaps at one of these is where you will begin a bushwhack off trail. Often a bushwhack is best planned to zigzag connecting one interesting checkpoint to the next on your way to the final destination. This not only eases navigation, it may include interesting intermediate destinations. The slight additional distance hiked is not all bad of course, since a few extra minutes visiting that beaver pond and dam checkpoint may become the highlight of the trip. Anything of significance that is permanent and uniquely identifiable is a good checkpoint.
Checkpoint Distance and Timing
Major checkpoints are handy when they are spaced not much more than 20-30 minutes apart along your route. On most hikes it is not difficult to find obvious and distinctive checkpoint terrain features when either on trail or bushwhack that will serve your navigation requirements well. Planning with a map lends to thinking in terms of distance. Hiking in the field better lends to thinking in terms of time, as in "how much longer before I reach the lake?" Checkpoints are best defined by thinking in terms of time spacing rather than distance. How much distance is between 30-minute checkpoints? Of course there's no easy answer, but there are general guidelines. Only your own personal experience in a variety of terrain conditions will tell you your own pace and speed. The good news is your hiking plan is designed to be dynamic, flexible according to real encountered conditions. The actual rate and timing will change from the original plan once you actually get into the hike. All you have to do is recognize the difference and adjust your navigation time estimates. This ability improves dramatically based on information you gain from your own previous similar experiences. Eventually you will accurately estimate actual arrival times to within a minute or two over 20 minute spans.
Travel Rates and Math
As a rough estimate, a fit hiker wearing a backpack on fairly smooth dry flat straight trails moving right along will walk at around 3 mph for a few miles. This pace will probably not maintain that high all day, especially while stopping to enjoy the view or study a beaver dam. Add a few twists and turns and a water break or two and our hiker is down to a leisurely 2 mph pace. Rougher trail and moderate up and down undulations decrease the speed to 1.5 mph, which is also a fair rate when bushwhacking over reasonably good untracked terrain. Encountering witch-hobble brush, blowdown, and swamps rapidly decreases speed to 1 mph or less. Sweaty crawling through dense thickets or constant clambering over severe blowdown can get you way down to a quarter of a mile per hour. Of course steep uphill trudges will considerably decrease your speed as well, even on good trail. Your mileage will vary, these are not necessarily the speeds you will maintain all day, but are good to use as planning estimates between checkpoints. With experience you will develop a good feel for how fast you are moving along in various terrain types.
The quick math of a 3 mph hike puts a 20-minute checkpoint one mile away, and a 30-minute checkpoint at a mile and a half away. One and a half mph terrain halves the distance or doubles the time. Intermediate speeds and distances do not require a calculator or pencil, just practice at estimating simple relationships off the top of your head. For example, while hiking at what you feel is 2 mph to a location estimated to be _ mile away will take... less than 30 minutes (corresponding to 1 mile) but more than 15 minutes (a half mile). Somewhere half way between 15 and 30 minutes would be about right. If you guessed between 20-25 minutes you'd be correct. You will eventually develop the ability to look at two points on a map and say to yourself, "22 minutes".
You will want to fill in the distance gaps between major checkpoints by frequently applying terrain association techniques with map to keep on track. It is amazing that once you determine your own travel rate in the field, you will be able to look at the next section of route on the map and predict your arrival at the next checkpoint to within a couple of minutes. This is useful to navigation on trail, and hugely useful for navigation off trail.
As a final must-do planning task, be sure to write out your primary planned route with expected timing including any potential alternate side trips. After you have finalized the pre-trip plan leave a copy of your itinerary, including local authority phone numbers, with a responsible person not going on the trip with you. But before all of this you must study the map. "Make no little plans; they have no magic to stir men's blood" - Daniel Burnham
This is crucial, do not take this task lightly. Map study could be the single most important part of your entire expedition, saving you miles of exhausting and frustrating mistakes, or worse. It may take a couple of hours or more to do a proper job of pouring over your route. Establish the major checkpoint locations and pay particular attention to recognizing them, especially at turn points and areas that may be confusing, such as trail intersections. Best to begin early and to repeat studying sections of your planned route often over several days. Your first impressions will not be your last and the more you look the more you will understand about the map and the environment of your planned hike. "I may stray once in a while, but I stay pretty close to the map. I tend not to wind up in Australia when I'm heading for Portugal." - David Eddings
Fortunately map study is an enjoyable task, whisking you to places in your mind you have not yet seen before you actually get there. Memory of those places not yet seen will come in handy and save time and effort when you actually arrive. Ideally the objective is to put as much important map detail into your head as will fit. Memorize major feature shapes and directions by association of one feature relative to another rather than as isolated entities. Keep in mind that the impressive somewhat nearby mountain peak may not always be as visible or useful as are more nearby features. Look for boundaries created by long running ridges, valleys, flowing watercourses and charted trails or roads. Know the relationships and relative directions of one to the other. Memorize enough of the map so as a minimum you may recall major terrain features and directions that will lead you out in case you lose your map and other gear in the bush. Your pack with all your equipment could be stolen by a bear... such things have happened. Imagine being five miles from the closest public road with nothing but the clothes on your back. Maybe you have kept your compass in your pocket or around your neck, maybe not. Are you hopelessly lost? Not if you have done your map study, paid attention to mental notes made along the way, and can calmly use your wits. "Alone! Alone! No beacon, far or near! No chart, no compass, and no anchor stay!"- Ada Cambridge
Once you have chosen the major route checkpoints on the map, continue your at home map study by beginning at the trailhead and try to create a 3D mind picture of how you expect the terrain to look in all directions. In effect you are creating a continuum of checkpoints to navigate from by visual observation. Include in your picture the road you arrived on, where else it goes, and any other roads bounding or entering the area where you will be hiking. Near or far, are there any prominent man made or natural features in the vicinity of the trailhead that could be visible from the anywhere on the planned route, or stumbled upon if you have lost the route? Remember that in forested cover you can see much less far during summer leaf season than after the leaves have fallen. If a feature is not directly visible because of trees or intervening terrain, how about from a nearby elevation or clearing that might be shown on the map? These mental notes could guide you back if the feature is also visible from elsewhere along your route. Continue this visualization process from the map view for every route segment between major checkpoints until you reach your destination, then turn around and do it again on the mental return trip. Terrain may look surprisingly and completely different when seen from the reverse direction. Do the same thing when you actually get there, turn around frequent to look behind you at the return view, at critical landmarks commit the picture to memory. "It is not down in any map; true places never are." - Herman Melville
Hike Day, Hit the Trail
You're all packed and have arrived at the trailhead parking lot or other starting point ready to hike. Boots on, your gear is set and firmly strapped on your back, compass and map out and at the ready. They're cheap enough insurance, so always carry a spare compass in a different pocket and away from your primary compass just in case one gets lost. Carry a third small compass buried in your pack for a friend. We'll assume part of your trip is on trail; part is a complicated bushwhack deep into the wilderness. Your map is in a plastic map case or gallon size plastic zipper bag, folded up such that your route is visible. As you sign in on the DEC trail log you're confident you can locate and follow a memorized drainage route to a major road bridge even if you lose compasses and map.
Terrain Association and Observational Navigation
Munching a handful of energy releasing gorp, this is the time to take a gander around, to compare your map study 3D mental notes with what you see in 3D reality. Build some confidence in what you see compared to what you thought it would look like. Glance at your compass, roughly orient the top (north side) of your map toward that direction in space. Match terrain you see to corresponding features on the map. Don't be discouraged if your first impression of the landscape seems totally different from the map. Trees and brush on road berm can be more dense than you expected on the edges of large light open areas like parking lots. But when you focus down on the overall lay of the land and the direction slope and orientation of nearby terrain, you should be able to associate what you see on the map with the terrain you see in reality. This is terrain association, and along with observational navigation (ObNav) these are the methods at the core of precision land navigation. After a glance at your watch for the current time, a check of the sky for weather and the position of the sun, you're off for the first checkpoint of the day. "You can observe a lot by just watching." - Yogi Berra
Don't get lost on the subtle differences in terminology. Terrain association is the process of comparing what you see around you with what is depicted on the map, continuously translating the visual picture in 3D to the 2D representation on the map. As you move, the scene moves, both in the environment and on the map. ObNav is almost the same concept, except you rely more on persistent conveniently placed landscape features such as long ridges or ravines and streams that you want to parallel on your travel. ObNav refers you less frequently to the paper map, relying more on the map in your head of nearby easily followed prominent terrain. Climb a known ridge crest and "follow it easterly to the saddle then angle downhill left, northeast to the pond." Nature offers dozens of both the obvious (the sharp ridgeline you are following toward the mountain peak) and the subtle (the direction of the wind on your face or the sun at your shoulder). All together they form a collection of observable navigation clues for you to compile and track, in addition of course to reading your compass. "Not until we are lost do we begin to understand ourselves." – Henry David Thoreau
The Nitty Gritty Tricks of Terrain Navigation
So how do you really navigate when hiking in woodlands anyway? Continuous open mountain vistas are not what we experience here in eastern woodlands, so other less obvious terrain features must be used. Simply put, pay attention to all the clues, look for anything around you that changes. Think "change is your friend" for determining location. One of two things happens when you interact with a terrain feature; you may either pass it by or follow it. You can only pass by a point feature, but with a linear feature such as a ridge or river you may either pass by crossing it, or you can follow it toward your destination. If you follow, look for subtle changes along the way. Any change observed in terrain profile is good because each change in the landscape is another clue to tell you exactly where you are. Even lack of change serves as a clue that you are in the middle of a plain. Both change (undulating terrain) and lack of change (featureless flatland) are represented on a topographic map. Hiking in forested woods with hills and watersheds and all other kinds of terrain presents almost continuous change, making navigation very easy if you know what to look for and keep up with it as you pass each one. You just have to relate the visible location you see about you in the environment to the known location you see on your map, terrain association. Don't limit your observations to just the landscape. If the sun is at a certain angle off your shoulder, then it should stay on average at that angle when you are hiking on a reasonably straight path through the woods. The sun's movement across the sky is slow enough until you reset at the next checkpoint. Again, navigation is a dynamic process, taking into account all observations. The wind is trickier but still useful. If the wind is at your face at one point then it should stay on your face until you change your direction of travel. If not, then perhaps it is being influenced by local terrain, or maybe the weather is about to change. You should be aware of all changes and be prepared to explain rational causes of observed change including the wind. Each is one small clue working with all the rest in your bag of navigation tricks.
For example, you walk along a slope, paralleling a smooth moderate elevation ridge until eventually something different happens to it, it changes somehow. That landscape change will give itself away on the map if you look ahead. Maybe it is cut by a small ravine, just a slight break in its slope where water may flow during the wet season. That's a change in the smooth slope that will show up in both the real world to your eyes and under foot, and it will show up on your map as a slight squiggle to the parallel contour lines on the slope of the ridge slope. Perhaps there is a slight dip along the crest of the ridge before it continues on at its original elevation forming a terrain feature known as a saddle. Locate either of these feature changes and you have strong clues to your exact location.
Location clues from terrain changes take many forms. Coming up on a high elevation cliff, or a lake shore or a large river is obvious helpful change from much different terrain of a few minutes ago. Crossing a small intermittent stream or drainage, whether it has any water in it or not, or observing a local high point in a ridge you are paralleling are just as useful in disclosing your exact location. Ridges end, ravines begin, depressions appear. Observe the flow of streams you cross to see if they run toward your right or toward your left. Continuously describe what you see to yourself and relate what you see to the map. "The first two days, the country we met with was undulating with a gradual ascent to the west Southwardly at the distance of twenty or thirty miles appeared a range of high mountains bearing east and west." - William H. Ashley
Unmapped Woods Trails
In areas long ago logged you will come upon ancient trails where machinery and horses once skidded out timber. Sometimes there are mazes of intersecting trails twisting and turning in all directions, most eventually ending up nowhere at dead ends. In places they are grassy and open and easy walking. More often though they are choked with head tall prickly blackberry briars or thick with impenetrable saplings all competing for new daylight, often in rutted paths and looking quite different from the surrounding woods. They are tempting to follow because they are so distinctive, and portions may be heading in "almost" the right direction along your course. Often the easy walking sections are bordered by thickets, making it difficult to see through very far off beyond to the sides, obscuring ObNav. The choked sections are painful to walk through. Beyond that, there is another danger to be aware of in following unmapped trails. You are lulled into complacency by the trail's course being "almost" true to your intended course, and you tend to drop your ObNav awareness since travel may be temporarily easy. Your walking pace is different than that off trail, turns are frequent, and sweeping direction altering turns can be insidiously unnoticeable. Before you know it you've traveled distances and directions you never intended.
Grab a Handrail
A handrail is a feature that gives you precise knowledge of your position in one dimension, left or right of course. Try to follow terrain features that will lead you toward your destination or to any intermediate checkpoints. Use a linear terrain feature such as a watercourse, a ridge, a ravine, or perhaps a tree line or straight clearing edge as a handrail to guide you. The idea is to travel along or offset a short distance parallel to the handrail until you notice a terrain change, giving you location knowledge in the second dimension. Often you can traverse a broad slope at a certain contour level below a peak. Staying at one level along the slope gives you one-dimensional information, that you are following a line course. At some point sooner or later the contours will alter direction to go around the peak, or a ravine will cut down the slope, the contour line change thus cueing you to your 2D location. Following a known trail is a type of handrail navigation. You may not know precisely how far along the trail you are, but you know how far left or right of the trail you are walking (usually on it). It should be easy to find terrain changes the trail cuts through to provide the second dimension, giving you a precise location on the trail.
Saved by the Backstop
Most useful on a bushwhack, your planning should include looking for backstops a short distance beyond major checkpoints. This is important where a critical turn point is blind, indistinct, or hard to recognize and other navigation clues are few. If you miss the checkpoint and go too far, the backstop will tell you so. A large water body or long steep cliff, or a major trail perpendicular to your path on that leg are ideal backstops. Something as simple as a gentle but obvious change of broad terrain slope will do. If you reach the backstop it should be clear that you have gone too far and missed the checkpoint. Go back the way you came, or otherwise adjust your course only if you can determine exactly where you are.
An essential part of continuously knowing where you are, is to think ahead at what is upcoming next a short distance beyond your current view. When you drive for the first time on a freeway you must know in advance what road sign you expect to see and approximately how far ahead if you are to ever find your exit. You should have an expectation and observe with anticipation for the next feature change (the correct exit sign) to come into view. In the woods looking at the topographic map you might think such as: "in 10 minutes I should cross a small stream, flowing left to right." Just as essential is to follow up on this expectation of arrival. Thus if 12 minutes passes and you do not see the anticipated stream, then what? Perhaps you neglected to update your speed estimate because your path got significantly rougher. That would logically explain the extra time only if it was true. But what if you don't see the stream in, say, 15 minutes, could your time be that far off? Put your thinking cap on... rethink your last known location and your distance/time estimate. Did you miss the stream because it was dry that season; was there any hint of a dry drainage crossing a few minutes ago? Did you plan a backstop beyond this point? Look around where you are now. Does the general landscape still make sense with the map? If you think the map representing the stream was real and you cannot logically rationalize what happened to it, you must assume there is something wrong with your recent location assumption. You must figure out how you are going to resolve the problem before proceeding any further. Not to do so risks a compound navigation error, significantly increasing your confusion and wandering off intended course. "If you do not the expect the unexpected you will not find it, for it is not to be reached by search or trail." - Heraclitus
In a similar scenario, lets say you expect to come to checkpoint requiring a turn, for example to begin following a small stream. Based on actual hiking conditions you estimate it will take about 20 minutes to get there. Suddenly after only 13 minutes, there it is, a bonus, the stream - you've arrived early! If you do not question why you have arrived so early then you may be about to make a big mistake. This is a common navigation error. The vast majority of checkpoint arrival timing errors are made by estimating time too short, not too long. You usually think you are traveling faster than you do in reality. If you are surprised into thinking you have arrived early at the stream and cannot logically explain why, then most likely you are wrong in identifying that particular stream as your checkpoint. It's an easy thing to do if you are relying on an easily misidentified type of checkpoint. Recheck your map for signs of another stream, the one you are really at. Assimilate all the clues you see into the solution.
Don't Bend That Map
In the last example there is a great temptation to justify and accept your misidentified checkpoint rather than admit something is not quite right. Attempting to rationalize where you think you are in this way often results in what is known as "bending the map," when you adjust your assumed location to where you are really not, based only on what you "feel", even if not everything else observed makes sense to that adjustment. What has likely really happened is you crossed another indistinct stream prior to the checkpoint, one perhaps not explicitly shown on the map. Chances are if you carefully trace the contours then you will see the drainage feature and your timing to that point will make sense, as will other surrounding terrain features. Cross that false stream checkpoint to continue on to your original estimate, updated by actual travel conditions and speed, and you will find the real checkpoint as planned. Bending the map is easy to do, especially when you are tired and not thinking sharply. If unchecked, it fills your head with false assurances, rapidly leading to compound errors and potentially sudden panic. Compound errors are navigation mistakes based on previous mistakes, a difficult and bad scene to recover from indeed.
If on the other hand you have walked plenty far but you do not find a planned checkpoint and think you have somehow missed the obvious, you now have a few choices to make. First look around at your present position extremely carefully; study the big picture lay of the land, recalling where you have just been. While surveying the terrain, try to find a distinct tree or other marker object for your current location so you can continue to recognize this spot. Sometimes you may want to wander "just up to the nearby high ridge for a better view". You will only make your plight worse if you can't relocate the place where you first realized you were confused - be sure to use your compass. If you are confident that within a few minutes you can retrace steps to your last positively known position, going back to the place last known may be the best option. If you are panicked and don't have a clue where you are or where you came from, then get comfortable, sit down with your map and compass, have a snack and think hard. If you cannot figure out where you are then stay put instead of straying way off your itinerary. If it's getting late, think about shelter and arranging to signal for help instead of aimlessly wandering about. Time to think and study the map may save the trip and yourself. In the worst case, this is why your itinerary was left with a responsible person.
The Hypothesis Method of Navigation
In the general course of hiking along, if the terrain does not obviously shout out your location at you, it is still possible to find your exact location by gathering clues provided by visible features and changes in your surroundings. From these observations you make the hypothesis, "the clues seem to point to ‘here', a specific location on the map". But you are not 100% sure. Lets say by ObNav you think you are at a certain location. This "guess" is the hypothesis to be substantiated. If it is true, then any and all other clues you can find from the map should also fall into place. Look for them on the map, they are there. Maybe for example the map indicates there should be a gentle general drop off in an easterly direction, becoming steeper toward the north. Look around, is that terrain clue revealed and does your hypothesis continue to make sense? Can you see a mountain through the trees in the distance, and if so, should it be there, does it have the right shape and slope you expect from reading the map contours? Have you recently crossed a ravine, how long ago, how far back, what direction does it flow? Many small running streams are not indicated by a thin blue line on the map, but contour line waves crossing the ravine will give a clue to presence of a drainage bed. From your last confidently known position, could you be at your guessed location based on dead reckoning direction and speed? Every confirmed clue increases the probability that you are correct. When you accumulate several clues that all make sense together, you can assume your hypothesis is correct... or not. With experience you will know how confident you can be with all the clues you have available.
Don't Bend That Map Revisited
The hypothesis method is powerful and brings up a strong caution... if even just one observed terrain feature does not fit the hypothesis, then either the hypothesis or your observation is wrong. It is not necessary to identify the feature by name, you only have to apply terrain association. Do not ignore mismatches and be tempted to press on. It is amazing how many people will disregard mismatched terrain clues, especially when hot and tired from a long hike. Force fitting obvious terrain features to where they do not appear on the map (or vice versa ignoring unassociated map features that should be visible) is again "bending the map". This will rapidly get you into big trouble. Beaver ponds and dams may come and go, but only where there is evidence of a level wet area, never on a slope. Mountains, steep ravines, and prominent ridgelines simply do not appear or disappear over reasonable time. Stop, have some gorp and water, think over the situation, do not proceed any further until you completely understand what is going on. Go back the way you came to the last checkpoint you thought you identified if you cannot explain the reason or resolve the situation. Perhaps that checkpoint was wrong. "A man should look for what is, and not for what he thinks should be." - Albert Einstein
When Clues Are Scarce, Dead Reckon
Arrival at a beginning patch of flat featureless terrain is a good ObNav clue, but after you get a few minutes away from the edge (the region of change), further good clues may be elusive. Dead reckoning (DR) is always an ongoing navigation technique, no matter what else the situation and environment favor as a primary method. DR is no more than a means to estimate current position, advancing a known previous position by using course, time, speed, and distance traveled. In flat featureless unchanging terrain under heavy tree canopy or in extensive jumbled blowdown DR may be all you have. Fortunately in most normal recreational hiking areas careful attention to DR works quite accurately to get you to more varied hiking terrain. Soon enough the terrain will change to become ObNav friendly again. DR was often the only navigation means available for long distances by sea and air navigators in the time before the advent of persistent global electronic navaids. It worked for them over hundreds, even thousands of miles. "Dead Reckoning: You reckon correctly, or you are." – an aviator's quote
Fill In The Gaps As You Go
Unfortunately not all checkpoints are where you want them, and not all are equally or uniquely useful. You are about to realize that intermediate checkpoints abound and are extremely helpful. You don't have to wait for the major checkpoints you identified during map study at home. The goal is to continuously observe and let the terrain tell you where you are at all times - ObNav. Fill in the gaps between major identifiable checkpoints with minor features that make sense all along your route. You will get the "feel of the land" by being immersed in it, something you don't get from map study alone. Between checkpoints you read the general terrain, look for change and anticipate what's next. A place where the terrain breaks into a slight slope is enough to notice change. Sometimes the major checkpoint you choose during map study turns out not to be as obvious as it you had hoped. Recognizing any landmark point will be much easier if you have developed the skill to continuously monitor your location, almost as if you had one checkpoint after the other very closely spaced. "You've got to be very careful if you don't know where you are going, because you might not get there." - Yogi Berra
Discover the Compass
Up to this point the discussion has ignored precision compass reading. The compass was used to get you going in the right direction, but map reading and ObNav by interpreting terrain features set your course and identified your exact position. Knowledge of time of day and watching the sun's position could potentially get you this far in direction finding. Add exacting use of a compass to ObNav as just one more method to the list of tricks you already have. "Truth lies within a little and certain compass, but error is immense." - James Agee
The earth is a giant magnet, with a north magnetic pole and a south magnetic pole. It is useful to think in terms of "magnetic field lines" streaming from pole to pole. The compass needle itself is a magnet. Freely rotating within its case, the compass needle aligns itself parallel to the earth's magnetic field lines, and thus points north/south (note that natural iron deposits, nearby cars, and belt buckles may locally bend and disturb the normal direction of the earth's magnetic field lines). Usually the north-seeking end of the compass needle is painted red and/or may be shaped into an arrow. All in-the-field direction finding with compass is based on measuring angles clockwise from magnetic north, 0-359 degrees. That's all there is to it, a natural reference line on the earth always available to us, simple and powerful. "Only by staying where you can watch every turn of the prow can you retain a definite notion of north and south. And that is how it happened that, being unobservant of turns, I found the sun setting in the east-- a vexatious thing to a woodsman." - Nessmuk, Cruise of the Sairy Gamp, Forest and Stream, Sept. 13, 1883
Orienteering Compass Design
There are many different types of compasses. What is called the "orienteering" style has its roots in the old military style lensatic compass. A modern orienteering compass is easy to identify, inexpensive, and easy to use. It will have a rectangular flat clear plastic baseplate. Mounted to the baseplate is a circular rotating housing (bezel) containing the magnetic needle, usually filled with a viscous liquid to damp out the needle's rapid freedom of motion and help it move smoothly. The housing rotates on the baseplate; around the edge of the housing is an azimuth dial marked in degrees of angle. An arrow is inscribed or printed fixed to the bottom of the rotating housing, independent from the magnetic needle. A number of "orienting lines" will be spaced parallel to the inscribed arrow, fixed and rotating with it on the bottom of the housing. A fixed direction of travel arrow is inscribed on the baseplate, against which you read the azimuth on the rotating dial. Various measurement scales may be inscribed on the edges of the baseplate. The most important parts of the compass are the straight edge baseplate with direction of travel arrow, the rotating azimuth housing with orienting lines, and of course the magnetic needle. A slightly more advanced design is the folding mirror compass. It looks similar and has all the exact same features as the orienting compass just described, plus the sighting mirror. It normally can be used in the same manner as the standard model, with mirror folded out flat.
Some compasses will have a tiny brass or aluminum declination adjustment screw, either on the bottom of the compass or on top along the azimuth/bezel ring. A small brass (non-magnetic) piece of metal will be attached to the lanyard of such a compass. It is the screwdriver. Turning the screw will rotate the bottom of the bezel dial separate from the azimuth angle indicator. By setting this to the declination angle you can make your direction of travel angle read relative to True North instead of Magnetic North. More on this topic to follow. "No memory is ever alone; it's at the end of a trail of memories, a dozen trails that each have their own associations." - Louis L'Amour
The Compass in Use, Measuring an Azimuth
A compass primarily does one thing. It measures angles. The angle measured clockwise between magnetic north and whatever is the distant object of interest is its "magnetic azimuth", sometimes also known as "magnetic bearing". The azimuth defines a straight line between two objects on the earth. The path you take to reach a distant object, straight line or not, is your "course". Once you begin to travel along a measured azimuth, the "heading" you take is now called your "bearing" along a "course". The fine differences in semantics are more important to marine and air travel, and are less important for us here.
It is important to correctly hold the compass for best accuracy. There is only one correct way to hold a compass, do it this way every time. Be sure you identify the baseplate with the direction of travel mark or arrow on it, the orienteering arrow printed on the bottom of the rotating dial, and the magnetic needle within the dial housing. Most important is to squarely face your body toward the object you are measuring. Locate the direction of travel line or arrow printed on the baseplate. With the compass held flat in your hand at between waist and chest level, point the baseplate and direction of travel arrow at the object you seek. The direction of travel arrow must always point straight out of your chest. Make the measurement at chest level; don't try to be more accurate by bringing the compass up to your eye level. Look up at the distant object, face it squarely, drop your gaze line down to the compass. Do not chase the magnetic needle or try to turn the baseplate or your body to align or match it - keep the baseplate and your body pointed at the distant object. Now turn the housing dial with your other hand such that the printed orienteering arrow on the housing becomes perfectly covered by the magnetic needle, keeping the baseplate pointed at the object. This is called "boxing the needle", because the needle covers the box outlined by the printed orienteering arrow in the housing. Note there are two ways to align the needle; one is 180 degrees out from the other. Just be sure to match the red (north seeking) end of the magnetic needle with the north (arrow point) end of the orienteering arrow. Look at the mark where the direction of travel line touches the azimuth ring and read the azimuth value. The baseplate and direction of travel arrow are still pointed toward the object you seek as long as the needle is boxed over the orienteering arrow.
As an aside, if you want to exactly reverse the compass azimuth direction to return to your previous position you can follow a "back azimuth". Hold the compass in your hand, rotate your body and compass as a whole (do not separately rotate the azimuth dial) so the red (north) end of the needle boxes over the tail of the arrow. You will now be facing 180 degrees from the original destination, on a course back to the previous checkpoint. "The great thing in the world is not so much where we stand, as in what direction we are moving." - Oliver Wendell Holmes
Navigate by Compass Azimuth
Lets say you are standing on a mountainside clearing with a view and want to hike to a small pond you can see in the distance down below. You know that as soon as you step down hill and away from the clearing you are unlikely to see the pond through heavy dense brush and trees until you actually reach its shoreline. Using only the compass you can dead reckon your way to the pond easily (in practice you would combine with ObNav techniques for improved confidence and accuracy). Sight on the pond and box the needle in the compass. When you step into the woods and no longer see the pond, you need to stay on the azimuth defining your course to the pond. Properly hold the compass in front of you with the direction of travel arrow pointing away from your chest. Turn your gaze to the azimuth dial. Rotate your entire body and compass as a whole, do not touch the azimuth dial, to once again "box the needle". Repeating, do not turn the dial; rather turn your entire body with compass in hand to align the magnetic needle with the orienteering arrow. Before you continue, do a sanity check on your azimuth measurement. Make an estimate of how far away and how long it will take you to reach the pond. Using whatever knowledge you already have of your relative location from other navigation clues including map, terrain, and sun direction, which general direction is the pond from you? Does the azimuth you read on the compass dial make sense with what you already know about general directions? Have you accidentally turned the azimuth dial since you set it? Is the sun staying at approximately the same angle from you as you hike toward the pond?
You are now standing in the woods below the clearing, pointed toward the invisible pond with the your body and compass properly oriented. Lift your gaze from the direction of travel arrow to find some nearby object you can easily walk to along the course line. It might be a tree or rock or just a strange looking branch, anything that you can walk to without losing sight of it. Put your compass down and walk to that nearby sighting tree, avoiding logs and mud holes if necessary along the way. Upon reaching the sighted tree, hold the compass up again, orient your body to box the needle, find the next tree or rock or whatever you can see along the direct course to the pond. Repeat the sighting process until you reach the pond. As you approach the time and distance when you expect to be at the pond, ObNav terrain association should confirm you are getting close. Finally you see the glint of water threading through the tree leaves and you are there. It just works. "We were so far back in the woods, they almost had to pipe in sunlight." - Roy Rogers
If the pond is small, the terrain is difficult, and your experience not great, you may need a backup plan so not to bypass the pond without seeing it. Don't forget about the backstop concept in case you miss and overshoot the your destination. Ponds and other target destinations often offer a better technique. Look on the map for a linear feature perpendicular to your course, say an inlet or outlet stream from the pond, maybe a trail, or perhaps a ridge ending at the pond. You could offset your course slightly left or right, knowing you will come across the offset feature at some point easier than hitting the small pond directly. Aim your azimuth to the broad offset, say a couple of hundred yards to the left of the pond. When you reach the offset feature, you know you have to turn right, following the terrain directly to the pond. How far away from the target you set the offset depends entirely on experience and confidence level with that type of terrain.
The same technique is very handy for finding your car parked on a road after a trip into the woods. If your direct course aimed at the car results in a small error, arriving at some place on the road with no car in sight, which way would you turn to find it? If you walk the road in the wrong direction, how far will you go? With an intentional offset aim point miss you would know whether to turn left or right on the road. After a short walk in the known direction you arrive at your car. "All you need is the plan, the map, and the courage to press on to your destination" - Earl Nightingale
Which North is it?
It is almost time to bring in precision compass and map techniques to work together as a team. Before that you have to understand map orientation and declination. Most maps people are familiar with are oriented with "north" up, toward the top of the map. This is geographic north, the north you immediately know how to find on a globe of the earth, also called "true" north. The north and south geographic poles define the axis upon which the earth spins out our days. Meridians of longitude converge toward the north and south geographic poles, while parallels of latitude run perpendicular to the meridians. The left and right edges of a topographic map are meridians of longitude, the top and bottom are parallels of latitude. If you look carefully, you will notice a slight convergence of the map from top to bottom. The left and right edges, if followed in a straight line far enough, would meet at a point at the north (and south) geographic pole. "Now my eyes are turned from the South to the North, and I want to lead one more Expedition. This will be the last... to the North Pole." - Ernest Shackleton
Unfortunately, the geographic North Pole is not in the same place as the magnetic north pole. Your compass senses the direction to magnetic north, not to geographic north. The difference can be negligible in some places on the earth, but is more likely very significant, even extreme. The magnetic north pole is actually an indistinct region located some 800 miles away from the geographic pole, currently in northern Canada. It is on the move, wandering by several miles per year, destination unknown. In order to interpret a map (printed oriented relative to geographic north) in regards to a free-floating compass needle direction (which seeks magnetic north), it is necessary to know the current relative angle between the two kinds of "north".
Imagine a map of the earth looking down on the northern hemisphere with both the geographic and the magnetic poles plotted as points spaced some distance apart. A third point on the map (your location) completes three points of a triangle. If you face toward geographic (map) north, then magnetic north could be some angle to your left, or to your right, or even behind you if you are located in the extreme far north. This angle is called your "declination." It turns out that for the United States the dividing line between magnetic north being left and magnetic north right is a line that goes approximately through Chicago and Tallahassee. On the east coast then, magnetic north is to your left if you face "map north". On the west cost magnetic north is to your right as you face "map north". The angle of magnetic north in Maine is approximately 20 degrees left of map north, in Washington State it is approximately 20 degrees right. Every topographic map in the legend will tell you exactly how many degrees left or right for the region of that map. Unless the angle is near zero, you must take this angle into account for accurate navigation by compass with map. That's all you really need to understand. Declination maps are readily available, showing the declination angle for every place on earth. The lines connecting places of equal declination (think of these as magnetic meridians) tend to be curves, more complicated as you approach the poles, rather than straight lines. Every topographic map has the declination value of center map in the legend, either in a small diagram on the bottom or written on the side. On most maps of the scale we use for hiking in the U.S., declination is approximately the same over the entire map.
If magnetic north is so important, why aren't maps set up oriented to magnetic north instead of geographic north? Two primary reasons: The magnetic pole wanders, changing the angle to it over time. The magnetic meridian lines are not straight lines so they couldn't be used to everywhere simultaneously orient a large scale map. It just wouldn't work as well as using the straight lines of geographic longitude meridians. "Anyone who isn't confused really doesn't understand the situation." - Edward R. Murrow
Quantifying Course Angle Error, True North to Magnetic North
Ignoring declination of course results in compass navigation error. How much depends both on the magnitude of declination in azimuth, and on distance traveled. As a rule of thumb, each degree of error in azimuth (from whatever the reason) results in cross track error of 1/60th of the distance traveled. For example, one degree of error over a mile hike (5,280 feet) results in missing a blind checkpoint by a little less than 100 feet (5,280/60=88). That's not too bad, but it's only one degree of error. In the Adirondacks if the ignored declination is 15 degrees, the error jumps to almost a quarter mile horizontal error for every mile hiked. If you happened to apply declination in the wrong direction, doubling your error, you will be a hopeless half-mile offset from your goal that was originally a mile away. Of course combining ObNav and terrain association techniques would never let you get very far into the error. Use all of nature's clues! "If you cry 'forward', you must without fail make plain in what direction to go." - Anton Chekhov
Adjusting for Declination
Understanding how to adjust for declination often strikes fear into inexperienced backwoods navigators. They try to learn "east is least, west is best", or some other such confusing saying that has been with us for ages. Forget the math and the sayings. Use what you now know about the relative picture of magnetic and true north angles in your mind and logic instead. Just remember which side of Chicago you are on then pick an easy example. If you are on the U.S. east coast, magnetic north is to the left of true north. Therefore the compass azimuth angle is larger if measured clockwise from magnetic north than if it is measured from true north; larger by the declination angle. If you are in the mountain or western states, magnetic north is to the right of true north, so a clockwise magnetic north angle is smaller than is the angle measured from true north. The mind picture tells you if you think about it. It doesn't matter if the object you view is a little bit to the right (clockwise) in azimuth of north or almost all the way around at 300 degrees clockwise, the logic is the same. However, with more advanced techniques of magnetic meridian reference lines and a little preparation, not even this adjustment logic is necessary when you are hot, tired, and mentally spent on a mountainside. "A well adjusted person is one who makes the same mistake twice without getting nervous." - Alexander Hamilton
Orienting the Map to True Earth
It is handy for terrain association to orient the map to terrain features on the real earth, or the "field". This is especially handy on mountaintops with good views of surrounding distant terrain. Usually you can do this by rough observation, rotating the map to match what you see visually. Sometimes you can be quite precise if you can see distinct terrain features and rotate the map to match. Terrain associate those you see with those on the map, rotating the map to align it to the earth. Without easily associated terrain features you have to use something else as a reference. You can do this with great precision with your compass. But the north/south lines on the map (its edges) know nothing of magnetic direction. You must compensate for declination. This is not a problem if you keep in mind the declination diagram picture. Place the opened map on the ground or any flat surface well away from ferrous (magnetic) metallic objects. Stay away from vehicles, and don't use picnic tables with nails or screws in them. Rotate the map so that the top of the map is roughly toward geographic north on the earth. Find the local declination from the map legend. The whole idea now is to recreate the map's declination diagram using the long edge of the compass and the magnetic needle.
To do this, turn the azimuth housing (bezel) to dial in the local declination under the direction of travel line. In the Adirondacks this is usually between 12 and 15 degrees; dial that number into the azimuth ring. Find a flat spot on the ground away from all metallic objects (vehicles especially). Do NOT place the map on a table, as the screws and bolts in the table may have a severe negative effect.
Place one of the long edges of the compass baseplate on either the left or right edge of the map (precisely lining the edge along a geographic true north meridian). Do not further adjust the compass or rotate the housing. Now, rotate the entire paper map with compass resting on the map, compass and all, until you box the needle. Stand back and look at what you have. The compass baseplate edge is on the printed map edge, and the needle exactly overlays the orienteering arrow. The angle you see between the magnetic compass needle and the edge of the baseplate should look the same as the angle in the legend declination diagram. Magnetic north to magnetic north, true north to true north. If the picture looks backwards (as it would west of Chicago), you need to dial the angle 360 minus declination angle into the azimuth. Repeat the compass riding on map rotation of the map to box the needle, check the similarity to the declination diagram, and you have it.
Once the map is precisely oriented to earth, you can do some amazing things. Stand over the map in a position "behind" your present location, point your finger to your location on the map. Look for a distant mountain peak the map. Stand over the map, looking toward the distant object on the map. Raise your finger straight up off the map to the horizon and there's the mountain on the exact same line. You can do that for any number of objects you see in the distance and on the map, perfectly identifying each one of them. Details follow on the next page. "Happiness is a direction, not a place." - Sydney J. Harris
Detailed procedure to align-map-to-earth with a compass that has NOT been
pre-compensated for declination with an adjustment screw
Azimuth ring bezel is dialed to the declination angle, set under the "direction of travel" line on the compass. Get proper east/west rotation of bezel direction by looking at the map's declination diagram - with the direction of travel line as TN (the edge of the compass on the edge of the map), simply make the compass look like the declination diagram. In the eastern states you would dial in the declination directly (west of Chicago it is 360 minus declination). Place compass on map with the edge of the compass on and parallel to the edge of the map. If you have done it correctly, the orientating arrow within the rotating housing should now be offset in the same direction as MN on the map's declination diagram. Now rotate the entire map (with compass riding on the map) to box the needle with the orientating arrow. All compass azimuth angles measured to an object on the earth will now equal the corresponding angles to the object as depicted on the map. The compass will measure azimuths with respect to Magnetic North. Note the angle similarity of TN/MN on the map's declination diagram corresponding to the appearance of the compass – this is a check on the correct declination setting. If the angles look askew, recheck for the direction that the declination was dialed. See the graphic below:
Detailed procedure to align-map-to-earth with a compass that has been precompensated
for declination with an adjustment screw
Dial in the bezel "N" (360) under the "direction of travel" line on the compass. Using the adjustment screw and the tiny brass or aluminum "screwdriver" on the lanyard, adjust the orienting dial to the local declination. The red orienting arrow will no longer point to "N"; instead it will point to an angle offset by the declination. Be extremely careful here - which way to turn the screw? - Just match the adjustment angle to look like the declination diagram on the map. In the eastern states you adjust the orienting arrow to point at 360 minus the declination (point it at the +declination value if in the western US). See the diagram below and read on. Now place the compass on the map with one compass long edge aligned to the edge of the map. Rotate the entire map (with compass riding on the map) to "box the needle" with the orientating arrow on the baseplate. All compass azimuth angles measured to an object on the earth will now equal the corresponding angles to the object as depicted on the map. The compass will measure azimuths with respect to True North. Note the angle similarity of TN/MN on the map's declination diagram corresponding to the appearance of the compass - this is a check on the correct declination setting. If the angles look askew, recheck for the direction that the declination was rotated by the adjustment screw. See the graphic below, noting the differences in the orientating arrow and azimuth setting from the previous uncompensated case:
If the topo map has a UTM overlay grid, as most newer editions now have, you may use any of the north/south grid lines instead of the edge of the map as your True North azimuth reference. Note, however, that there is a potential error of up to 3 degrees with this method, although greatest error only occurs at high latitudes above 60 degrees north (or south). This small difference between grid north and true north will be shown as part of the declination diagram on maps that have the grid overlay. More on this later.
Map Feature to Earth
This lets you use the map and compass together to identify objects, either from map to earth or from earth to map. For example, you see a pond in the distance. Face the pond, hold the compass baseplate correctly, point the compass direction of travel arrow at the object, and turn the azimuth dial to box the needle (be sure to match red end of needle to red end of arrow, not the opposite). Once set, do not turn the azimuth dial again. Place the compass on the map with one of the compass baseplate corners on your location on the map (a corner closest to you, not one on the farther direction of travel side). Keeping that corner on your location, pivot the entire compass by rotating of the baseplate and compass as a whole (do not separately adjust the azimuth dial) to once again box the needle. The edge of the compass will define a line from your current location (under the pivot corner) directly toward the object you saw. The object you sighted will be on the line formed by the baseplate edge (or an extension of the line if the object is very far away and the baseplate too short). Note that the edge of the compass is used instead of the centerline along the direction of travel arrow. You will get the same answer if you center the compass instead of using a corner and edge, but it is more difficult to see what is hidden under the compass. Use the baseplate edge instead, it works exactly the same. Using the edge makes it easier to draw the line to the observed object.
Earth Feature to Map
Now reverse the process. Lets say you have limited view from your woodsy location, but since you know approximately where you are, you can fairly certain you can identify a mountain you see in the distance. This is a good application of the hypothesis method. Place the map on the ground and orient the map to earth using compass and declination compensation just as described above. Face the mountain, point the direction of travel arrow toward it, box the needle by turning the azimuth dial. Place the compass down on the map, this time using a forward end baseplate corner in the direction of travel, not the corner nearest to you. Pivot the entire compass (don't touch the dial housing or move the map) about that baseplate corner, keeping the corner on the mountain, as you box the needle. The long edge of the baseplate now defines a line between the mountain and your location. Your location is someplace on that line of position (including an extension of the line). Other ObNav clues should help narrow the exact spot.
Resection (Triangulation) To Find Exact Location
If by good fortune you can see and identify another mountain in a different direction, do the same thing over again with the second azimuth. You will have two lines of position crossing at some point. The only place you can simultaneously be on both lines at the same time is if you at the crossing point. Accuracy improves if the two observations are nearly 90 degrees apart, or with sighting on additional terrain features at different angles. This technique is commonly called triangulation, but more properly is resection.
Remember that you only have to consider declination compensation once with this technique, at the time you orient the map to ground. In this case the map is a perfect representation of the earth in your vicinity. As such, the earth's magnetic field aligns with the map exactly the same way it does with the real terrain. The compass is used in its natural magnetic mode as you visually sight objects in the terrain by holding it up to the real earth. That angle is no different on the oriented map. Placing the map on ground to orient it for long distance vistas is helpful and instructive. But doing this each time you want to check an azimuth is tedious and unnecessary, especially when in the thick of it and no views are to be had. A better method exists, discussed below.
Map Magnetic Meridian Reference Method
There is a way to completely eliminate the need to orient the map to ground and still use the compass directly in magnetic mode on and off the map. It requires simple preparation at home; at the time you are doing your map study anyway. All you do in essence is rotate the map so that magnetic north is up, and draw a few lines that run magnetic north/south, substituting orienting the map to magnetic north instead of geographic north. You will then be able to ignore the edges of the map that run geographic north/south. This transforms the map from a geographic longitude meridian reference, to a magnetic meridian reference. This is just what your compass wants, and all you have done is to rotate the map by a few degrees of declination to a new angle reference. Over the coverage of a topographic hiking map the declination value and direction is approximately constant. That means you can draw a straight line on the map at the declination angle and use it as the new angle of reference.
Purchase an inexpensive protractor anywhere you find school supplies. It is a plastic semicircle with angular measurement on the arc and a ruler on the diameter (in a pinch your compass is also a small protractor and can be used as one). Place the protractor on the edge of the map, rotate it to the declination angle, and use the straight side with a yardstick against it to draw a long line on the map. Draw parallel lines all across the portion of interest on the map, about an inch apart. You will be accurate enough to carefully eyeball the yardstick parallel from one line to the next, drawing lines a stick width apart. Before you begin do a sanity check on the angle. You should note the similarity to the lines and angles on the declination diagram in the legend of the map (if it has a diagram). Caution, do not simply extend the magnetic north line of the tiny declination diagram, it will not be accurate enough. But the diagram and your lines should look similar, true north straight up, your map drawn magnetic lines and the magnetic north line of the diagram at the same angle. Be sure you angle the protractor the right way to match the declination angle. It is easy to measure at the negative angle, but a glance at the diagram will check your work. Remember that east of Chicago the lines will tilt top left (magnetic north is toward your left). West of Chicago the lines will tilt top right (magnetic north is to your right). In the end you have a map with a series of parallel lines an inch or two apart, all aligned to magnetic north.
Compass and Map Together, Magnetic Meridian Reference
This is where this method shines and it all comes together. Once magnetic north lines are drawn on the map, the map is adjusted for declination whenever you next use it without worrying about declination math in the field. Orienting the map in the field to the earth is not necessary (though may be visually handy where views exist), but if you wish you can simply turn the map to align the drawn magnetic north lines parallel to a free compass needle. This procedure is shown in graphic form at the end of this paper. In fact, everything you need to know about map and compass together is contained in those two end pages.
There are two ways to use map and compass with this method. There is one simple rule with this method to keep from getting confused. When the compass touches the map, ignore the magnetic needle. Not until you lift the compass off the map do you use the magnetic needle to orient the compass and yourself to the actual azimuth direction on the earth. When the compass is on the map you will use the azimuth dial and the orienteering arrow and the parallel lines inscribed on the azimuth dial, along with the direction of travel arrow on the rectangular baseplate. Angles are measured relative to the magnetic declination lines you have drawn on the map. Remember, the compass needle is ignored when the compass is on the map.
Map Feature to Earth
Use this when you know your location on the map and you want to head toward some feature that you identify on the map at some distance and azimuth angle from your present location. The actual object may or may not be visible from where you stand. Say you see a pond on the map you want to visit that is not visible from your location. What course do you follow to get there? With magnetic north lines drawn on the map, the map need not be orientated at all, how you hold the map may a completely random orientation. You will use the compass azimuth dial (not the magnetic needle) referenced to the magnetic north map lines to find the azimuth and your course. As before, use the edge of the compass rather than the center because it is easier to use the edge, and you get the same answer. Place one corner of the compass nearest you on your known present position, and line up the compass edge on the pond, as if you were drawing a line from you to the pond with the compass edge. If your compass edge is not long enough to span the difference, either visualize extending the line or find a longer straight edge (ruler) and extend the compass edge with it. Once again, ignore the magnetic needle when the compass is placed on the map.
Now the key step... hold the baseplate of the compass firmly on the map with baseplate edge defining your course, from your position on the map to the pond on the map. The orientation of the map and the compass relative to ground has no significance whatsoever (because you are ignoring the floating needle). While holding the baseplate still, turn the azimuth dial to align the orienteering arrow (and its parallel inscribed lines) to be parallel with the magnetic north lines you have drawn on the map. Keep the baseplate stationary, ignore the magnetic Also be sure to use the red (north) end of the orienteering arrow to point toward magnetic north, not the other way around. Remember, ignore the magnetic needle in the compass housing for this step. The azimuth dial at the direction of travel line now reads the course direction to the pond – the azimuth angle information is saved on your compass.
Pick up the compass, do not rotate the dial from where it was set when it was on the map. Doing so will erase the information you have saved on it. Hold the compass chest high with the direction of travel arrow on the baseplate pointing directly away from your chest. Rotate your entire body until the magnetic needle is boxed, thus aligning the needle directly over the orienteering arrow at the bottom of the housing. Remember, now that the compass is no longer on the map, this is when you use the magnetic needle to box the needle by turning the compass as a whole. Do not spin the azimuth dial separately; only turn your body with compass in hand. Your body and compass turn as one single unit until the needle is boxed.
With the needle now boxed, raise your gaze to the horizon straight ahead, pick a distinctive tree and walk to it, repeat until you reach the pond. This is the course to the desired location, the pond you want to visit. Make sure what you are doing makes sense with all the other ObNav and terrain association clues about you. Proceed on course to the pond. "A few observations and much reasoning lead to error; many observations and a little reasoning to truth." - Alexis Carrel
Earth Feature to Map
As before, this process can be reversed to precisely fix your position. Use the hypothesis method to estimate your location. You sight on a presumed known distant mountain and use it to find a line of position to your location. Proceed as before, facing the mountain, point your compass baseplate and direction of travel line out of your chest toward the mountain. Now turn the azimuth dial to box the needle, thus preserving that azimuth information on your compass. Place the compass on the map with the baseplate corner that is away from you pivoting on the mountain. Ignore the magnetic needle when the compass is on the map. The information regarding direction to the mountain is stored in the azimuth dial - so don't spin that dial. Rotate the compass with baseplate and dial as a whole on the map, pivoting about the baseplate corner placed on the mountain. Do not turn the azimuth ring from its set angle! Turn the entire compass to align the orienteering arrow (and its parallel lines) to the magnetic north lines drawn on the map, pivoting about the baseplate corner held on the mountain. When the orientating lines look parallel to the magnetic north lines on your map, the compass baseplate edge will form a line directly from the mountain to your location. Repeat for other distant objects at other angles, where the lines cross is your precise location on the map. This spot should make sense with other ObNav clues.
This technique is robust enough to be done on the move as you are hiking. If your map is properly folded to cover the area of interest, you can sight objects, put compass to map, and mentally draw the lines of positions on the map to confirm your estimated position even as you are moving. Of course you are using this technique in combination with ObNav and terrain association for additional navigation aids.
Alternative Method: UTM Grid Reference to Measure Azimuth
If your topographic map has a UTM overlay grid, as most newer editions now have, you may use any of the grid north/south lines (GN) instead of drawing magnetic north lines on the map. Assuming the GN lines are parallel to TN, then all measured azimuth angles will be relative to True North. Note this is not quite perfectly accurate. There is a potential error of up to 3 degrees with this method, although greatest error only occurs at high latitudes near 60 degrees north. At lower latitudes the difference is usually less that one degree. This small "grid declination" difference between grid north and true north has nothing to do with magnetic declination, it is only an artifact of referencing to a square grid over a spherical earth. The exact difference between grid north and true north will be shown as part of the declination diagram on maps that have the grid overlay. ObNav should mitigate small compass errors.
With a declination compensated compass: If your compass is compensated for declination by using the adjustment screw, you may use any of the north/south grid lines as a measurement reference. The procedure is otherwise identical to using the hand drawn magnetic north reference lines. Azimuth reference will be relative to True North (approximately).
With an uncompensated compass (warning, math made easy with thinking involved): If your compass is not compensated for declination the same procedure of using GN lines for azimuth reference will work, but unfortunately declination math is now involved. Before taking your measurement from map to earth, or from earth to map, you MUST compensate for magnetic declination. The map is set relative to TN. Your compass is set to measure MN. The best way to remember whether to add or subtract declination from azimuth is to always think of the declination diagram and how the map would appear if you had drawn the parallel MN lines. Do this earth to map thought exercise: Picture yourself facing a real world object that on your uncompensated compass happens to be exactly at 0 degrees MN. What direction is this relative to TN? In the east, just remember (from the diagram) that to get to 0 degrees MN from 0 degrees TN you have to turn some number of degrees (the declination angle) to the left of the 0 degree TN reference lines. If you are going to plot this object on a map that only has TN reference lines, you must convert your compass's MN reference azimuth into a TN reference azimuth. So you would subtract the declination (let's say it is 15 degrees) from 0. Therefore 0-15=360-15=345 degrees True azimuth. From your location on the map, plot the object on a line of 345 degrees measured relative to TN (or any GN line). As another example, an object measured on your compass is at 40 degrees MN azimuth. Plot it from your location on the map at 40-15=25 degrees relative to the TN (or GN) lines. It is not terribly difficult if you keep the declination diagram in mind and of which angle measured clockwise would be greater.
Now for the reverse process of going from map to earth with this GN reference technique using an uncompensated compass. Recall the declination diagram and recall how magnetic lines drawn on the map would appear if you had drawn them. What you measure on the map with an uncompensated compass from GN is an angle that is not large enough, compared to measuring it from MN lines. Do this: Measure the edge of the map (or along any one of the GN vertical lines). Remember, the rule is that you ignore the needle when compass touches map (except for the special case when you are orienting the map to earth). Turn the bezel to align the orienting lines on the bottom of the dial to parallel the lines on the map. What do you get for an azimuth? You should of course be reading 0 degrees TN azimuth. But if you had measured from the MN lines you had drawn on the map, you would be measuring the declination angle as the azimuth relative to magnetic north, lets say 15 degrees. Therefore, whatever value you get from measurement off the map has to be increased (in the eastern US) by the declination before you can take that measurement from map to earth. To walk in a 0 degree TN direction you must add 15 to the azimuth taken off the map measurement (which in this case was 0 degrees). Taking it one step farther, if you measured an angle from the map (using the GN reference lines) of 25 degrees, you must then add the declination (recall the diagram) to get the magnetic reference to dial into your compass. You would dial into your compass and walk toward 25 + 15 = 40 degrees magnetic.
From the above description, using a compass that is not compensated for declination on a map that does not have magnetic north lines drawn may seem complex. It is not if you keep the picture of the declination diagram as you of how think to get from MN to TN.
Practice Practice Practice
None of the techniques described here are at all difficult if you understand them in small increments. Successful and enjoyable backcountry navigation is a conglomeration of techniques, assembling many clues of various types provided by nature. The information is all there. It's how you put it together that makes it easy and natural. Practice is the key to improvement. Mistakes will be made, but with experience, precision in navigation will improve.
"In the adventure known as life there are those that live it vicariously and enjoy the ride from the safety of their armchair, and that's good. There are those who have a few chances to realize the incredible life changing experience and though they don't repeat them, they carry a growth and personal philosophy for the rest of their lives. And there are those whom for a taste is never enough, for whom the lust of adventure is nearly insatiable. And if you add to that the overwhelming desire to create and share, then you get where I was, at the end of one adventure it only signifies the beginning of another." – Les Stroud, Survivorman, 02.22.09